Expandable vertebral implant

ABSTRACT

A joint spacer therapeutically maintains separation of bones of a joint. A carriage is slideably retained within the frame and has at least one ramped surface. An actuator screw is threadably engaged with the frame, and rotatably connected to the carriage, to cause the carriage to slideably move within the frame when the actuator screw is rotated. First and second endplates engage the bones of the joint, and each has at least one ramped surface that is mateable with the ramped surface of the carriage, whereby when the carriage is slideably moved by rotation of the actuator screw, the endplates ramped surface slides against the carriage ramped surface to cause the endplates to move along an axis transverse to the longitudinal axis of the frame, to increase the height of the spacer. Piercing elements are connected to the carriage to pierce bone of the joint when the carriage is moved.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/270,620, filed Sep. 20, 2016, which is a continuation application ofU.S. patent application Ser. No. 13/711,204, filed Dec. 11, 2012.

This application is also a continuation of U.S. patent application Ser.No. 15/270,620, filed Sep. 20, 2016, which is a continuation-in part ofU.S. patent application Ser. No. 14/940,322, filed on Nov. 13, 2015,which is a continuation of U.S. patent application Ser. No. 13/845,645,filed on Apr. 3, 2013, now U.S. Pat. No. 9,216,095, which is acontinuation-in-part of U.S. patent application Ser. No. 13/451,230,filed on Apr. 19, 2012, now U.S. Pat. No. 8,518,120, which is acontinuation-in-part of U.S. patent application Ser. No. 13/440,158,filed on Apr. 5, 2012, now U.S. Pat. No. 8,679,183, which is acontinuation-in-part of U.S. patent application Ser. No. 13/273,994,filed on Oct. 14, 2011, now U.S. Pat. No. 9,358,126, which is acontinuation-in-part of U.S. patent application Ser. No. 12/823,736,filed on Jun. 25, 2010, now U.S. Pat. No. 8,685,098, which is acontinuation of U.S. patent application Ser. No. 12/579,833, filed onOct. 15, 2011, now U.S. Pat. No. 8,062,375. The disclosures of all arebeing incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to stabilizing adjacent vertebrae of the spine byinserting an intervertebral spacer, and more particularly anintervertebral spacer that is adjustable in height.

BACKGROUND OF THE INVENTION

Bones and bony structures are susceptible to a variety of weaknessesthat can affect their ability to provide support and structure.Weaknesses in bony structures have numerous potential causes, includingdegenerative diseases, tumors, fractures, and dislocations. Advances inmedicine and engineering have provided doctors with a plurality ofdevices and techniques for alleviating or curing these weaknesses.

In some cases, the spinal column requires additional support in order toaddress such weaknesses. One technique for providing support is toinsert a spacer between adjacent vertebrae.

SUMMARY OF THE INVENTION

In accordance with the disclosure, a joint spacer for therapeuticallymaintaining a separation of bones of a joint, comprises a frame havingdistal and proximal ends defining a longitudinal axis extendingtherebetween; a carriage slideably retained within the frame and havingat least one ramped surface, the carriage further including a threadedportion; an actuator screw threadably engaged with the frame, theactuator screw configured to bear against the carriage to cause thecarriage to slideably move within the frame when the actuator screw isrotated; a first endplate configured to engage a first bone of thejoint, and having at least one surface mateable with the at least onecarriage ramped surface, whereby when the carriage is slideably moveableby rotation of the actuator screw, the at least one endplate rampedsurface slides against the at least one carriage ramped surface to causethe first endplate to move along an axis transverse to the longitudinalaxis to increase a height of the spacer; and a second endplateconfigured to engage a second bone of the joint.

In one embodiment thereof, the carriage includes at least two rampedsurfaces, and the second endplate includes at least one ramped surfacemateable with at least one of the at least two ramped surfaces of thecarriage, whereby when the carriage is slideably moved by rotation ofthe actuator screw, the at least one second endplate ramped surfaceslides against the at least one additional carriage ramped surface tocause the second endplate to move along an axis transverse to thelongitudinal axis to increase a height of the spacer.

In other embodiments thereof, the first endplate is configured to abutthe frame as the first endplate is moved along an axis transverse to thelongitudinal axis, whereby the first endplate moves substantially onlyalong an axis transverse to the longitudinal axis; the first endplateincludes at least one aperture through which a fastener may pass tosecure the first endplate to a bone of the joint; the spacer furtherincludes a blocking mechanism to prevent backing out of a fastenerpassed through the first endplate; and the first endplate includes oneor more projections configured to engage bone of the joint when theimplant is positioned between bones of the joint.

In further embodiments thereof, at least one of the first and secondendplates is composed of two interconnected portions of dissimilarmaterials; one of the dissimilar materials is metallic and includes atleast one aperture through which a fastener may be passed to attach theimplant to a bone of the joint; and one dissimilar material ispolymeric, and another dissimilar material is metallic.

In yet further embodiments thereof, the actuator screw includes aflange, and the carriage includes a flange rotatably mateable with theactuator screw flange; the spacer further includes a thrust washerinterposed between the actuator screw and the carriage; the spacerfurther includes a polymeric material configured to press against theactuator screw to reduce a potential for unintended rotation of theactuator screw; and the spacer further includes a plate having at leastone aperture sized and dimensioned to receive an elongated fastener forfastening the spacer to bone of the joint, the plate being releaseablydetachable from the spacer to reduce an profile of the spacer duringinsertion of the spacer into the body, the plate attached to the spacerinside the body.

In other embodiments thereof, the plate and the frame include matingportions of a twist-lock connector operable to connect the plate to theframe when the spacer is inside the body; the plate and the frameinclude mating portions of a snap-fit interference connector operable toconnect the plate to the frame when the spacer is inside the body; theplate includes hinged portions, the hinged portions foldable to reduce aprofile of the plate during insertion of the plate into the body; the atleast one surface mateable with the at least one carriage ramped surfaceis at least one ramp; the at least one carriage ramp is disposed upon atleast one cam, the cam rotatable to bear the at least one carriage rampagainst the at least one surface of the first endplate; the firstendplate includes a rotatable portion having first and second transverseaxes of different lengths; and the rotatable portion is passable throughan interior of the spacer.

In other embodiments thereof, the first endplate includes an aperturesized and dimensioned to receive an elongated fastener operable to passthrough the aperture to affix the spacer to bone of the joint, theaperture movable with the first endplate as the first endplate is movedalong the axis transverse to the longitudinal axis; and the firstendplate includes a first portion having at least one aperture throughwhich a fastener may pass to secure the first endplate to a bone of thejoint, and a second portion configured to support bone of the joint, thefirst and second portions mutually connected by a dovetail connection.

In additional embodiments thereof, the spacer further includes arotatable plate having at least two apertures through each of which afastener may pass to secure the spacer to a bone of the joint, therotatable plate rotatable after the spacer has been implanted within thebody, to overlie the at least two apertures with bone of the joint; thespacer further includes a rotatable plate having at least two aperturesthrough each of which a fastener may pass to secure the spacer to a boneof the joint, the rotatable plate rotatable after the spacer has beenimplanted within the body, to overlie the at least two apertures withbone of the joint; the spacer further includes at least one rotatableplate having an aperture through which a fastener may pass to secure thespacer to a bone of the joint, the rotatable plate rotatable after thespacer has been implanted within the body, to overlie the aperture withbone of the joint; and the spacer further includes at least two platesrotatably connectable to the spacer, each plate slidably connected tothe other by a dovetail joint, each plate having at least one aperturethrough which a fastener may pass to secure the spacer to bone of thejoint, the plates rotatable after the spacer has been implanted withinthe body, and each of the at least two plates slideable with respect tothe other, to overlie the aperture of each plate with bone of the joint.

In yet further embodiments thereof, at least one of the carriage rampedsurfaces is operative to push a piercing element through an aperture inthe first endplate, the piercing element operative to pierce bone of thejoint to secure the spacer within the body; the spacer further includesa bone screw having bone engaging threads and gear teeth, and theactuator screw including gear teeth engageable with the gear teeth ofthe bone screw, the actuator screw thereby rotated when the bone screwis threaded into bone of the joint; the spacer further includes a platehaving an aperture through which a fastener may be passed to connect thespacer to bone of the joint, the plate including a dovetail portion; andthe first endplate including a dovetail portion mateable with thedovetail portion of the plate, the plate and the first endplate therebysecurely connectable to each other; and the spacer further includes achannel formed within the first endplate, the channel sized anddimensioned to receive an elongate portion of a fastener operative tosecure the spacer within the body.

In other embodiments thereof, the spacer further includes at least oneelongate rotatable deployer pivotally connected to the frame; at leastone piercing element connected to the deployer, the at least onepiercing element operable to pierce bone of the joint when the rotatabledeployer is rotated within the body; the at least one piercing elementis pivotally connected to the deployer to thereby enter bone of the bodyat a desired angle relative to a plane of the first endplate; the atleast one rotatable deployer rotates about a common axis with respect tothe actuator screw; the at least one rotatable deployer rotates when theactuator screw is rotated; and the at least one rotatable deployerrotates independently of the actuator screw.

In yet further embodiments thereof, the first endplate is pivotallyconnected to the frame; the first endplate pivots about the pivotalconnection, about an axis extending transverse to the longitudinal axis;and the first endplate is connected to the frame to allow roll, pitch,and yaw movement of the first endplate with respect to the frame.

In another embodiment of the disclosure, a joint spacer fortherapeutically maintaining a separation of bones of a joint, comprisesa frame having distal and proximal ends defining a longitudinal axisextending therebetween; a carriage slideably retained within the frameand having at least one ramped surface, the carriage further including aflange; an actuator screw threadably engaged with the frame, theactuator screw including a flange rotatably mateable with the carriageflange, whereby the carriage is slideably moved when the actuator screwis rotated; a first endplate configured to engage a first bone of thejoint, and having at least one ramped surface mateable with the at leastone carriage ramped surface, whereby when the carriage is slideablymoved by rotation of the actuator screw in a first direction, the atleast one endplate ramped surface slides against the at least onecarriage ramped surface to cause the first endplate to move along anaxis transverse to the longitudinal axis to increase a height of thespacer; and a second endplate configured to engage a second bone of thejoint.

In various embodiments thereof, when the actuator screw is rotated in anopposite, second direction, the at least one endplate ramped surface isslideable against the at least one carriage ramped surface to cause thefirst endplate to move along an axis transverse to the longitudinal axisto decrease a height of the spacer; the first endplate includes ametallic portion having an aperture through which a fastener may bepassed for connecting the implant to body tissue, the first endplatefurther having a polymeric portion connected to the metallic portion,the polymeric portion sized and dimensioned to support a bone of thejoint; the frame and the first endplate include mateable dovetailedportions configured to maintain an orientation of the first endplate andthe frame when the first endplate is positioned proximate the frame.

In another embodiment of the disclosure, a method for therapeuticallymaintaining a separation of bones of a joint, comprises inserting aspacer between bones of the joint, the spacer including—a frame havingdistal and proximal ends defining a longitudinal axis extendingtherebetween; a carriage slideably retained within the frame and havingat least one ramped surface, the carriage further including a flange; anactuator screw threadably engaged with the frame, the actuator screwincluding a flange rotatably mateable with the carriage flange, wherebythe carriage is slideably moved when the actuator screw is rotated; afirst endplate configured to engage a first bone of the joint, andhaving at least one ramped surface mateable with the at least onecarriage ramped surface, whereby when the carriage is slideably moved byrotation of the actuator screw in a first direction, the at least oneendplate ramped surface slides against the at least one carriage rampedsurface to cause the first endplate to move along an axis transverse tothe longitudinal axis to increase a height of the spacer; and a secondendplate configured to engage a second bone of the joint; the spacerinserted when the first endplate is positioned proximate the frame; andslideably moving, by rotation of the actuator screw, the at least oneendplate ramped surface against the at least one carriage ramped surfaceto cause the first endplate to move along an axis transverse to thelongitudinal axis to increase a height of the spacer to maintain aseparation of bones of the joint.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings, in which:

FIG. 1 depicts a perspective view of a spacer in accordance with thedisclosure, including bone fasteners, the spacer in a reduced height, orcompressed configuration;

FIG. 2 depicts the spacer of FIG. 1, in an increased height, or expandedconfiguration;

FIG. 3 depicts a front view of the spacer of FIG. 1;

FIG. 4 depicts a front view of the spacer of FIG. 2;

FIG. 5 depicts a cross-section taken through a center of the spacer ofFIG. 2;

FIG. 6 depicts a top view of the spacer of FIG. 1;

FIG. 7 is a diagram of a possible implantation location in the body, forthe spacer of FIG. 1;

FIG. 8 depicts an embodiment of a spacer in accordance with thedisclosure, including a fixation plate that is removeably connectable toa remainder of the spacer, the fixation plate shown removed;

FIG. 9 depicts a connector for connecting the fixation plate to aremainder of the spacer, with respect to FIG. 8;

FIG. 10 depicts the spacer of FIG. 8, the fixation plate attached;

FIG. 11 depicts a reverse side of the spacer of FIG. 10;

FIG. 12 depicts a front view of the spacer of FIG. 10;

FIG. 13 depicts a side view of an embodiment of a spacer in accordancewith the disclosure, the spacer including a detached fixation platehaving a snap-fit attachment;

FIG. 14 depicts the spacer of FIG. 13, the fixation plate snap-fit intoattachment;

FIG. 15 depicts the fixation plate of FIG. 13;

FIG. 16 depicts a hinged fixation plate in accordance with theembodiment of FIG. 13;

FIG. 17 depicts the hinged fixation plate of FIG. 16, the hingedportions folded, and further showing barbs upon the hinged portion;

FIG. 18 depicts an embodiment of a spacer in accordance with thedisclosure, including cams operative to increase a height of the spacer,the spacer in a reduced height configuration;

FIG. 19 depicts the spacer of FIG. 18, the cams actuated to increase aheight of the spacer;

FIG. 20 depicts an embodiment of a spacer in accordance with thedisclosure, the spacer including rotatable endplate portions;

FIG. 21 depicts an end view of the spacer of FIG. 20;

FIG. 22 depicts the spacer of FIG. 21, the rotatable endplate portionrotated;

FIG. 23 depicts an embodiment of a spacer in accordance with thedisclosure, having endplates that translate together with endplates, asendplates are moved to increase a height of the spacer;

FIG. 24 depicts the spacer of FIG. 23, the spacer expanded to have anincreased or expanded height;

FIG. 25 depicts a side view of an embodiment of a spacer in accordancewith the disclosure, the spacer having connectable fixation portions andendplate support portions;

FIG. 26 depicts a cross-section of the spacer of FIG. 25;

FIG. 27 illustrates an embodiment of a spacer including connectablefixation portions and endplate support portions, the portionsconnectable by a dovetailed connection;

FIG. 28 depicts a cross-section of the device of FIG. 27;

FIG. 29 depicts an embodiment of a spacer of the disclosure, including arotatable fixation plate;

FIG. 30 depicts the spacer of FIG. 29, the fixation plate rotated;

FIG. 30A depicts an embodiment of a spacer of the disclosure, includingtwo rotatable fixation plates, rotated to a deployment position;

FIG. 31 depicts an embodiment of a spacer of the disclosure includingtwo rotatable fixation portions connected by a sliding dovetailconnection;

FIG. 32 depicts the spacer of FIG. 31, the fixation portions relativelydisplaced and rotated;

FIG. 33 depicts a cross-section the spacer of FIG. 31;

FIG. 34 depicts an embodiment of a spacer of the disclosure, includingdeployable piercing elements;

FIG. 35 depicts the spacer of FIG. 34, the piercing elements deployed;

FIG. 36 depicts an embodiment of a spacer of the disclosure, including abone fixation device having gear teeth mateable with gear teeth of anendplate actuator screw;

FIG. 37 depicts the spacer of FIG. 36, the bone fixation device deployedto engage bone, and to increase a height of the spacer;

FIG. 38 depicts an embodiment of a spacer of the disclosure, including adovetail connection between a fixation portion, and a bone endplatesupport portion;

FIG. 39 depicts the fixation portion of the spacer of FIG. 38;

FIG. 40 depicts the bone endplate support portion of the spacer of FIG.38;

FIG. 41 depicts an embodiment of a spacer in accordance with thedisclosure, including channels in endplate portions;

FIG. 42 depicts a top view of an embodiment of a spacer in accordancewith the disclosure having deployment arms rotatably supporting piercingelements;

FIG. 43 depicts a cross section of the spacer of FIG. 42;

FIG. 44 depicts the spacer of FIG. 43, the piercing elements deployed;

FIG. 45 depicts an embodiment of a spacer in accordance with thedisclosure, including a deployment arm having a common axis with anactuator screw;

FIG. 46 depicts a cross section of the spacer of FIG. 45;

FIG. 47 depicts the spacer of FIG. 46, the piercing elements deployed;

FIG. 48 illustrates an alternative spacer in accordance with FIG. 45,the deployment arm independently rotatable; and

FIG. 49 illustrates an embodiment of a spacer in accordance with thedisclosure, an endplate pivotable about a transverse axis.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments are disclosed herein; however, it isto be understood that the disclosed embodiments are merely examples andthat the systems and methods described below can be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present subject matter in virtually anyappropriately detailed structure and function. Further, the terms andphrases used herein are not intended to be limiting, but rather, toprovide an understandable description of the concepts.

The terms “a” or “an”, as used herein, are defined as one or more thanone. The term plurality, as used herein, is defined as two or more thantwo. The term another, as used herein, is defined as at least a secondor more. The terms “including” and “having,” as used herein, are definedas comprising (i.e., open language).

With reference to FIGS. 1-7, spacer 100 is operative, when positionedbetween adjacent bones of a joint, such as for example vertebrae 10, 12(shown in FIG. 7), to stabilize a joint formed between adjacentvertebrae. Spacer 100 has a collapsed state or height, illustrated inFIGS. 1 and 3, and an expanded state or height, illustrated in FIGS. 2,4 and 5. Spacers 100 of the disclosure may be inset into theintervertebral disc space at a collapsed height, and then expand axially(superior/inferior) to restore height loss in the disc space. Spacer 100provides distraction as well as achieves optimal separation of adjacentvertebrae, or disc height restoration. When inserted in a collapsedstate, Spacers 100 have a reduced height profile which reduces adverseimpact to tissue adjacent to and within the joint space duringinsertion, while presenting the least visually blocking or physicallyobstructing profile. Spacer 100 may be reduced in height afterimplantation, for example by inserting a tool through a minimalincision, to perform a therapeutic height adjustment. Spacer 100 mayalso be reduced in height to a compressed configuration, to facilitateremoval from the body. Spacer 100 supports the cortical rim of adjacentvertebrae, and distributes forces across the vertebra, therebymaximizing vertebral endplate preservation.

Spacer 100 includes two separable endplates 110, 112. A surface 114 ofan endplate 110, 112 can be provided with teeth or other projections 116which can penetrate body tissue to reduce a likelihood of migration ofspacer 100 after implantation. Spacer 100 is further secured with one ormore fasteners, such as bone screws 300, which pass through an adapter,such as bone screw socket 118 within spacer 100, and into body tissue ofthe patient. In the embodiment illustrated in FIGS. 1-5, two sockets 118for two bone screws are provided, although one or more than twofasteners and fastener adapters, may be provided. Bone screws 300 can beretained in connection with spacer 100 by blocking fasteners 120. Bonescrew 300 can be a polyaxial screw, and sockets 118 correspondinglyshaped, whereby bone screw 300 may be inserted into body tissue at anoptimal angle with respect to spacer 100, whereby optimal purchase maybe obtained, or certain body tissue may be avoided.

Endplates 110, 112 are moveably connectable to an actuator 150 operableto change a relative relationship of endplates 110 and 112. Actuator 150includes a frame 152 rotatably supporting an actuator screw 154, and amoveable carriage 156. As actuator screw 154 rotates within frame 152,carriage 156 slides within frame 152, driven by cooperation betweenthreads 158 upon actuator screw 154, and mating threads 160 within frame152. An implantation tool engagement surface 330 may be provided upon orwithin spacer 100, configured to receive a tool to enable securemanipulation of spacer 100 during implantation or removal from the body.

In the embodiment of FIGS. 1-6, endplates 110 and 112 are formed in twoconnected portions, including a portion 122, 122A which can bepolymeric, for example PEEK, and a fixation portion 124, 124A, which canbe metallic, for example titanium, although other materials may be used.For example, material used for fixation portion 124 should withstand thebending forces exerted by a fastener, for example bone screw 300,passing therethrough. In contrast, endplate material advantageouslyresiliently withstands a pressure applied by weight of the body. In thisregard, both materials could also be polymeric, for example, but ofdifferent types of polymer.

The portions 122, 124 or 122A and 124A are joined in the embodimentshown by screws, a mechanical interlock, adhesive, or other fasteners,possibly in combination, as explained further herein. Metallic portions124, 124A can provide greater strength for portions of spacer 100 whichare under relatively greater stress, for example portions through whicha fastener may pass to anchor spacer 100 within the body. While portions122, 122A, 124, 124A are described as polymeric or metallic, it shouldbe understood that other materials may be used, and that the portionscan be of similar or dissimilar materials, as described further herein.

With reference to FIGS. 1 and 3, it may be seen that spacer 100 is in acompressed state, having a lower height relative to an expanded state,as shown in FIGS. 2 and 4. A functioning of device 100 may be bestunderstood with reference to FIG. 5, which is a cross-section throughthe center of spacer 100. Endplates 110 and 112 are provided with ramps164, sized to slidingly receive ramps 168 disposed upon carriage 156.While three mating ramps 164, 168 are illustrated for each endplate 110,112, it should be understood that one, two, or more than three sets oframps 164, 168 may be provided. Mating ramps 164, 168 operate to enablea reduction or increase in height by sliding against each other asactuator screw 154 is rotated. Interlocking flanges 204, 204A rotatablycouple actuator screw 154 and carriage 156, whereby actuator screw mayrotate and advance or retard in connection with frame 152, concomitantlyadvancing or retarding carriage 156 along a longitudinal axis of spacer100 extending from a distal end 186 and a proximal end 182 of frame 152.A reduction in height is further fostered by a pressure exerted by bodytissue.

As may further be seen in FIG. 5, ramps 164 can include channels 164Awithin endplates 110, 112, and ramps 168 may include dovetail portions168A which extend into ramps 164. By projecting a dovetail portion 168Aof ramp 168 into channels 164A, endplates are moveably affixed tocarriage 156. Dovetail portions 168A and channels 164A may furthersupport a predetermined relative orientation of endplates 110, 112 whenin a compressed or expanded configuration, while they are beingexpanded, and when spacer 100 is inserted and removed from the body. Itshould further be understood that a relative orientation of endplates110, 112 may be substantially parallel, or may be non-parallel, forexample to produce an effective lordosis. Further, planes defined by aninterior portion of endplates 110, 112 may be relatively parallel, butbone contacting surfaces may be relatively non-parallel.

Carriage 156 is alternatively or further supported by frame 152 bylateral engagement means, in the embodiment shown there are two supportscrews 174 engaged with carriage 156, and passable through respectivechannels 176 formed in frame 152.

A hex driver (not shown) is inserted into engagement with an end ofactuator screw 154 at a proximal end 182 of frame 152. As actuator screw154 is turned, distal end 172 bears against a thrust washer 184, and anend portion of frame 152. As actuator screw 154 rotates in onedirection, carriage 156 is driven along actuator screw by interaction ofthreads 158 and 160 and flanges 204, 204A. As carriage 156 moves,endplates 110, 112 are urged to move along ramps 168, and 168A ifpresent, causing endplates 110, 112 to thereby moving relatively apart,and to increase a height of spacer 100. Endplates 110, 112 are movedrelative to carriage 156 by abutting against an end portion 186 of frame152. End portion 186 can include an internal ramped surface 170 mateablewith a ramp 168, as shown in this embodiment, thereby providingadditional stability in an expanded configuration.

In a given orientation, one of endplate 110 and 112 is an upper endplatewith respect to an orientation in a standing patient. However, spacer100 may, in some embodiments, be implantable in either of oppositeorientations, and therefore designations of upper and lower are providedfor ease of understanding, only. It should further be understood thatonly one of endplate 110, 112 may be moveable with respect to the other.For example, in one embodiment, ramps 168, 168A may not be provided, andendplate 112 may be attached to frame 152.

FIG. 7 illustrates a spacer 100 of the disclosure implanted betweenadjacent vertebrae 10, 12. Frame 152 defines a distal or leading end 186which is inserted first into the body, and a proximal or trailing end182 which passes last into the body, the distal and proximal endsdefining a longitudinal axis extending therebetween. Spacer 100 can beinserted into the body, and into a position between vertebrae, usingminimally invasive methods, for example using a small incision, andspacer 100 may be passed through a cannula or other structure whichmaintains a pathway through body tissue. Spacer 100 may be inserted intothe spinal column through any approach, including anterior,anterolateral, lateral, posterolateral, or posterior. A portion of thedisc annulus, and nucleus pulposus may be removed in order to form aspace into which spacer 100 may be inserted.

Spacer 100 can be inserted when configured to have a lower heightprofile, as shown in FIGS. 1 and 3, whereby an extent of distraction ofbody tissue may be reduced during insertion. Moreover, to the extentthat spacer 100 is used to open a pathway towards an implantation site,trauma to adjacent tissue is reduced relative to inserting a spacerhaving a final height profile. Once spacer 100 is positioned betweenadjacent vertebrae, actuator screw is rotated by a tool. The tool may bepositioned entirely within the body, or can extend from in interior ofthe body to outside the body, for example having a driving tip at oneend and having a handle at an opposite end, with a shaft extending intothe body between each end.

Once actuator screw 154 has been rotated to separate endplates 110, 112a desired amount, the tool is removed. At this point, actuator screw 154may be secured in place, for example using a mechanical block, or anadhesive, to prevent unintended rotation of actuator screw 154. Ascarriage 156 is slideably moved by rotation of actuator screw 154, ramps164, 168 of endplates 110, 112 slide against each other, to cause theendplate to move along an axis transverse to the longitudinal axis ofthe frame, to increase a height of the spacer. Rotation of actuatorscrew 154 in an opposite direction causes movement along an axistransverse to the longitudinal axis of the frame to decrease a height ofthe spacer.

In FIG. 6, it may be seen that spacer 100 has an elongated, narrowprofile, facilitating insertion from a lateral approach. Bone ingrowthapertures 332 may be provided, to promote the ingrowth of bone of thepatient to further stabilize spacer 100, or to achieve fusion, shouldthat be a therapeutic objective.

Polymeric insets, or a polymeric square nut, for example PEEK, can beprovided, engageable with threads 158 or other portion of actuator screw154, to provide additional friction to prevent height loss under load,particularly under cyclic loading. Similarly, once bone screws 300 havebeen inserted, blocking elements 196 may be rotated to extend over anend of bone screw head 302, preventing screw 300 from backing out. Toenable insertion of bone screw 300, a notched portion 196A is formed inblocking element, and which may be rotated into a position adjacentaperture 118. A similar mechanical block (not shown) may be provided foractuator screw 154.

With reference to the figures, it may be seen that sockets 118 move withendplate 110 or 112, as spacer 100 expands to a final height, wherebysockets 118 overlie cortical bone of vertebrae 10, 12 after spacer 100is expanded.

In an embodiment, spacer 100 of the disclosure provides an actuator thattranslates relative to the body by means of a threaded actuator screw154. Ramps 168, 168A on a carrier 152 mate with ramps 164, 164A onendplates 110, 112. Linear translation of carriage 152 causes endplates110, 112 to expand spacer 100 along an S/I axis with respect to thebody.

In one embodiment, two bone screws 300 are used to provide fixation intoadjacent vertebral bodies, a screw extended from each of endplates 110and 112. Spacer 100 can thus be narrow, to therapeutically fit betweenvertebrae when inserted from a lateral approach. However, one screw, ormore than two screws 300 may be used. Bone screws 300 can have sphericalor otherwise curved heads, facilitating insertion at a desired angle, ormay be provided to mate with socket 118 in a fixed orientation, forexample depending on a diameter of a neck portion of screw 300. Cam typeblocking fasteners 196 can be used to block bone screws 300 from backingout after being inserted.

Referring now to FIGS. 8-12, a spacer 100A is similar to spacer 100,however a fixation plate 210 is rotatably fastened to a collar 212extending from frame 152A. The collar includes an interlock 214, in theexample shown a twist-lock connector, although any means of mechanicallyfastening fixation plate 210 to the remainder of spacer 100A may beused, provided that fixation plate 210 and actuation screw 154 may berotated as described herein. Fixation plate 210 enables spacer 100A tobe inserted into the body with fixation plate 210 rotated to have alongitudinal axis aligned with a transverse axis of spacer 100A, wherebythe combined spacer 100A and fixation plate 210 may have a reducedheight, and whereupon a reduced sized incision may be used to implantspacer 100A with fixation plate attached. After implantation, fixationplate 210 may be rotated, for example about 90 degrees, so that sockets118 overlie bone of adjacent vertebrae. Rotation may be any amount,however, for example 45 to 135 degrees.

Alternatively, spacer 100A may be implanted without fixation plate 210attached, and through a reduced size incision, with less disturbance tobody tissue. Fixation plate may then be attached to spacer 100A in situ.In this manner, fixation plate 210 may be inserted through the sameentry as spacer 100A, with fixation plate 210 aligned along alongitudinal while being passed through the incision. Once positionedproximate spacer 100A, fixation plate 210 may be reoriented to beattached to spacer 100A, and rotated to align sockets 118 with bone.Rotation of fixation plate 210 can be performed after expansion ofspacer 100A, facilitating alignment of sockets 118 with bone.

It should be understood that the various embodiments described hereinwith respect to spacer 100 and frame 152 may be applied equally tospacer 100A and frame 152A, and any other variants thereof describedherein, and are described separately only to facilitate an understandingof each embodiment. More particularly, various embodiments of thisdisclosure are intended to be combinable in a manner that would beapparent to the practitioner and therapeutic for the patient.

In one embodiment, fixation plate 210 may only be attached to spacer 100when a longitudinal axis of fixation plate 210 is substantially alignedwith a transverse axis of spacer 100, and when fixation plate 210 isrotated to overlie bone, fixation plate 210 is securely affixed tospacer 100. For example, in FIG. 9, an embodiment of interlock 214 isillustrated, including flanges 216 which engage mating flanges 218disposed upon fixation plate 210. Flanges 216, and or the matingflanges, can be ramped or cammed, so that when engaged, fixation plate210 and spacer 100 become progressively more tightly interconnected.

In another embodiment, shown in FIGS. 13-17, fixation plate 210 ispreliminarily held in place using a snap-fit connector 220, functioningto secure fixation plate to spacer 100, or cooperating with interlock216. Snap-fit connector 220 forms at least a preliminary connectionbetween fixation plate 210 and spacer 100, to facilitate handling by themedical practitioner. A plate mounting screw 334 may be connected, forexample threaded into a threaded bore of actuator screw 154, to furthersecure fixation plate 210 to a remainder of spacer 100. Fixation platemay be rotated when connected by snap-fit connector 220. Set screws 226may be passed through apertures 226A to affix fixation plate 210 once ithas been rotated. Snap fit connector 220 comprises extension tangs 222extend from spacer 100, and form a resilient interference fit withsnap-fit aperture 224 upon fixation plate 210. Snap-fit aperture 224 maybe formed upon spacer 100, and extension tangs may extend from fixationplate 210. Additionally, references to spacer 100 should be consideredto include similar embodiments, including spacer 100A.

With reference to FIGS. 16 and 17, fixation plate 210A includes, inanother embodiment of the disclosure, folding or hinged portions 228which may contain sockets for bone screws 300 or other fastener. Wheninserting fixation plate 210A, hinged portions 228 are folded either ona lateral, longitudinal, or other axis of the fixation plate along oneor more hinges 230, as shown in FIG. 11, to reduce a maximum dimensionalprofile of fixation plate 210A. In this manner, fixation plate 210A maypass through a reduced size incision as compared to a requirement for anunfolded fixation plate. In an embodiment, tangs or barbs 232 may extendfrom fixation plate 210 or 210A. to engage body tissue, for examplecortical bone of a vertebra, to provide further fixation and stabilitywhen bone screws are passed through the fixation plate and into bodytissue. Additionally, hinged portions 228 may be angled to permit a bonefastener passed therethrough, for example bone screw 300, to enter boneof the joint at a beneficial or desired angle.

Referring now to FIGS. 18-19, one or more expansion cams 240 aredisposed between endplates 110, 112. A tool is inserted into a socket242 which may be rotated to rotate the cam (as shown by arrows) toseparate endplates 110, 112. Expansion cams 240 can be supported upon ashaft (not shown) connected to frame 152. Endplates 110, 112 can besupported and guided by ramp channels 164A, 168A, as described withrespect to FIG. 5.

Turning now to FIGS. 20-22, in an alternative embodiment, endplates 110,112 include one or more rotating endplate sections 250A, 250B whichengage body tissue to therapeutically increase a height of spacer 100B.In the embodiment shown, two rotating endplates sections areillustrated, each containing a transverse dimension having a firstwidth, and a second longitudinal dimension having a second, greaterwidth. Spacer 100B can be inserted into the body with sections 250A,250B rotated to have a same or lesser height than a remainder of spacer100B, to reduce an incision size, and to fit within an opening formedbetween adjacent vertebrae. After spacer 100B has been positionedbetween vertebrae, sections 250A, 250B may be simultaneously orconsecutively rotated to contact body tissue, for example cortical bone,to distract the joint. Section 250B is disposed on a proximal side ofspacer 100B, and may be rotated by inserting a tool, for example tool252, through or into a mating socket 254, and rotating tool 252.Sections 250A, 250B are rotatably coupled to spacer 100B by a pivotshaft, which may be engaged by tool 252, or by another mating engagementbetween section 250A, 250B and a remainder of spacer 100B, for example aflange (not shown).

Section 250A is inserted first into the body, and to facilitateinsertion, and to reduce interference with body tissue, section 250A maybe rotated so that section 250A and a remainder of spacer 100B form acompressed or unexpanded profile. For example, section 250A is rotatedso that the longest dimension is transverse to an S/I orientation in thebody, and is thus adapted to fit within a space formed between adjacentvertebrae prior to distraction. To distract the joint, tool 252 isinserted into an interior of spacer 100B, and is engaged with a socket254 associated with section 250A, and is rotated to orient section 250Aso that a tallest dimension is aligned with an S/I axis of the patient,distracting the joint.

With reference to FIG. 20, in one embodiment, section 250A fits betweenendplates 110, 112 when rotated in the transverse orientation, tofacilitate insertion between vertebrae. After implantation, section 250Ais pushed distally to emerge from between endplates 110, 112, whereuponit may be rotated to distract, aid in distraction, or maintain aseparation of vertebrae. Tool 252 is connected to section 250A by atether 256, operative to maintain section 250A in contact with aremainder of spacer 100B, in cooperation with a biasing element 258,disposed within tool 252. In FIG. 20, section 250A is illustrated inthree stages of insertion, illustrated by 250A-1, 250A-2, and 250A-3. Inthe first stage, illustrated as 250A-1, tool 252 is engaged with section250A and begins pushing section 250A along an interior of spacer 100Bdefined between endplates 110, 112. In the second stage, illustrated as250A-2, tool 252 has pushed section 250A to an end of an interior ofspacer 100B. In the third stage, illustrated as 250A-3, tool 252 haspushed section 250A to emerge from between endplates 110, 112, whereupontool 252 may then rotate section 250A to orient a long axis of section250 along an S/I orientation within the body. Tether 256 may be securedwithin spacer 100B to maintain section 250A in position at a distal endof spacer 100B. Tool 252 may then be disengaged from spacer 100B andremoved from the patient. FIG. 21 illustrates section 250A orientedtransverse to an S/I orientation, to reduce a height of spacer 100B.FIG. 22 illustrates section 250A rotated to distract or maintain aseparation of vertebra. Projections 260 can be provided, oriented topierce body tissue to foster maintenance of a position of spacer 100within the body.

Referring now to FIGS. 23-24, fixation portions 124, 124A separaterelative to each other as endplates 110, 112 are expanded as describedherein. In this embodiment, fixation portions 124, 124A can slideablymate with an actuating section 208, or may only be affixed to theirrespective endplate 110, 112. One manner of forming a slidable matingconnection is described with respect to FIGS. 31-33, herein. Byremaining in a fixed position relative to their respective endplate 124,124A, portions 124, 124A are properly aligned to secure a fastenerthrough socket 118 into cortical bone of adjacent vertebrae 10, 12.

In FIGS. 25-26, a manner of connecting endplates 110, 112 to fixationportions 124, 124A is illustrated. Fixation portions 124, 124A andendplates 110, 112 are mutually shaped to be mateably connected, forexample by a coupling fastener 262, in this embodiment a screw. In theembodiment shown, endplate 110 and fixation portion 124 are illustrated,however it should be understood that a similar or different connectionmechanism may be employed for endplate 112 and fixation portion 124A.

A similar connection between endplate 110 and fixation portion 124 maybe seen in FIG. 27, in which it may also be seen that screw 300 can becountersunk within fixation plate 124. Socket 118 may additionally be apolyaxial socket, and can include a blocking element 196. FIG. 28illustrates that the in addition to, or in an alternative to the use ofcoupling fastener 262, endplate 110/112 and fixation portion 124/124Amay be joined by shaped coupling, for example a dovetail,tongue-in-groove, or T-connection. As an alternative to couplingfastener 262, an adhesive may be used, or alternatively, the shapedcoupling may produce an interference fit between endplate 110/112 andfixation portion 124/124A. While FIG. 28 illustrates fixation portion124 (or 124A) inserted within endplate 110 (or 112), it should beunderstood that this configuration could be reversed, with endplate110/112 inserted within fixation portion 124/124A.

In FIGS. 29-30, fixation portions 124, 124A swivel so that socket 118can be positioned over cortical bone of a vertebra 10, 12. In theillustration, portions 124, 124A are connected, or are formed as asingle rotating fixation plate 266, and rotate together about a singlepivot. In FIGS. 29-30, the pivot is centrally located about the sameaxis as actuator screw 154, however the pivot may be located elsewhere.In one embodiment, an endplate pivot pin 274 extends between an endplate110/112 and plate 266, causing plate 266 to rotate about the centralaxis as endplate 110/112 is moved with respect to the central axis.Alternatively, as illustrated in FIG. 30A, fixation portions 124, 124Amay be separate, and each pivot on its own pivot, 264, 264A. In thisembodiment, as well as other pivoting embodiments, one or more endplatepivot pins 274 may be provided to cause a controlled rotation of arotatable plate, for example one or both of separated plates 124, 124A.

With reference to FIGS. 31-33, rotating fixation plate 268 is formed intwo slidingly mateable plates 268A, 268B. An exemplary interconnectionbetween plates 268A, 268B is illustrated in FIG. 33, in which a dovetailor interlocking engagement 270 may be seen. In this embodiment,interlocked plates 268A, 268B are secured in connection with a remainderof spacer 100, and rotate about, a pivot 272. In one embodiment, pivot272 is associated with actuator screw 154. In a related embodiment,rotation of actuator screw 154 causes a rotation of plate 268 due to amechanical connection between actuator screw 154 and plate 268. Inanother embodiment, pivot 272 is formed coaxial with, but separate fromactuator screw 154.

Referring now to FIGS. 34-35, blades, spikes, pins, or piercing elements276 are disposed within piercing guides 278 formed within spacer 100,for example within endplates 110, 112. Only relevant portions of spacer100 are illustrated in FIGS. 34-35, to clarify this feature of thedisclosure. In one form, piercing element 276A passes through a portionof ramp 164, and is pushed by ramp 168 as actuator screw 154 is rotatedto engage mating ramps 164, 168. Piercing element emerges throughendplate 110 or 112 to pierce body tissue, for example cancellous orcortical bone of adjacent vertebrae 10, 12. In this manner, spacer 100is further affixed in a therapeutic location within the body. Byproviding additional fixation in the form of piercing elements 276,spacer 100 is better adapted to function without supplemental support,as a standalone device, without for example other fixation or fusingdevices. Additionally, piercing elements herein can provide sufficientfixation so that a fixation portion 124, 124A can optionally beeliminated, and fixation exterior to the intervertebral space may beavoided.

In another embodiment shown in FIGS. 34-35, piercing element 280 isformed as a resilient curved member which is straightened as it ispushed by a portion of carriage 156. During straightening, piercingelement 280 elongates to pass through endplate 110, 112 to pierce bodytissue.

In FIGS. 36-37, bone screw 300A is formed with gear teeth 282 disposedto lie along a longitudinal axis of the screw, as well as standard boneengaging threads substantially transverse to this longitudinal axis.Actuator screw 154A includes external gear teeth 284 mateable with gearteeth 282 of bone screw 300A, whereby when either bone screw 300A oractuator screw 154A is rotated, endplates 110, 112 separate to increasea height of spacer 100, and bone screw 300A is simultaneously driveninto body tissue to therapeutically secure implant 100 to bone.

FIGS. 38-40 illustrate a method of connecting endplate 110/112 tofixation portion 124/124A, using a mortise and tenon or dovetailconnection 286. A keyed aperture 288 disposed within fixation portion124 or endplate 110 mateably receives a correspondingly shapedprojection 290 in the other of fixation portion 124 and endplate 110. Asimilar connection may be formed between fixation portion 124A andendplate 112. Aperture 288 and projection 290 may form an interferencefit, or may alternatively be secure in mating conformity using a setscrew or adhesive, for example.

With reference to FIG. 41, it may be seen that one or both of endplate110, 112 may be beveled, truncated, fenestrated, or shaped with a gap,groove, or channel 292 in endplate 110, 112, dimensioned to permitpassage of a bone screw 300, whereby a maximum height of spacer 100,with the exception of bone screw 300, is defined by an expanded heightof endplates 110, 112. Channel 292 can allow passage of a shank 294, orany other portion of bone screw 300 or other fastener, so that socket118 does not lie at a height greater than an endplate 110, 112.

Turning now to FIGS. 42-44, an embodiment of the disclosure includes oneor more piercing elements 276A, pivotally mounted to rotatable deployers310. Piercing elements 276A may have any shape which is adapted topierce, grip, or engage body tissue, including pin, spike, or bladeconfigurations. Although drawn as separate blades in FIG. 42, it shouldbe understood that elements 276A may extend along a substantial lengthof a longitudinal axis of spacer 100, and may be supported by one, two,or more deployers 310. An axle, pin, or shaft 296 pivotably mountsdeployer 310 to frame 152, carriage 156, or other mounting point ofsuitable strength, upon spacer 100, so that deployers 310 may rotateabout a longitudinal axis aligned with a longitudinal axis of spacer100, although mounting along a different axis can be provided. In FIGS.42-44, spacer 100 is illustrated without endplates 110, 112 andassociated ramps, to simplify the illustrations. It may be seen,however, that ramps 164, 168 may be reduced in size to allow room forone or more deployers 310.

In use, a tool (not shown) is engaged with an engagement port 198 and isrotated to rotate a deployer 310, to advance piercing element 276Athrough an opening or gap in an endplate 110/112. In one embodiment,piercing element 276A is fixed to an end of deployer 310, and entersbody tissue at an angle with respect to a plane defined by an endplate110/112. In the embodiment shown, piercing element is pivotally mountedto deployer 310 at pierce pivot 312, and can be guided, for example byguide 314, which may be a shaped channel in endplate 110/112, to enterbody tissue, for example bone of a vertebra 10/12, substantiallyperpendicular to a plane defined by an endplate 110/112, or at aparticular desired angle or within a range of angles. Piercing elements276A therapeutically secure implant 100 to bone or body tissue of thejoint.

FIGS. 45-47 contain elements analogous to FIGS. 42-44, however deployer310 rotates about a common axis with actuator screw 154, and thereforerelatively larger ramps 164, 168 can be maintained. Piercing elements276B may further be longer, as a length of an arm 316 of deployer 310Amay be longer.

In FIG. 48, a collar 320 is connected to deployer 310A, and rotatesabout a common axis with actuator screw 154, but may be rotatedindependently of actuator screw 154 using tool engagement port 322. Inanother embodiment, actuator screw is directly connected to deployer310A, and causes deployment of piercing elements 276A as endplates 110,112 are expanded as described herein. In a yet further embodiment,actuator screw rotates deployer 310A through a gear reduction (notshown), whereby deployer 310A rotates about the common axis more slowlythan actuator screw 154, so that increased leverage may be applied topiercing elements 276A.

With reference to FIG. 49, in an embodiment of the disclosure, endplates110, 112 can pivot about an axis 324 extending transverse to alongitudinal axis of spacer 100, or along an axis that extends along anS/I direction when spacer 100 is implanted within a patient. Forexample, one or more pivot pins 326 may extend from an endplate 110 toframe 152, or may extend from endplate 110 to endplate 112. In thismanner, spacer 100 may accommodate an additional rotational degree offreedom, for example, spacer 100 may support six degrees of freedom ofmovement of adjacent vertebrae. This is accomplished in one embodimentby enabling movement of ramped surfaces 164, 168 with respect to eachother, thereby enabling roll, pitch, and yaw of endplate 110/112 withrespect to frame 152. While rotation about this axis is explicitlysupported in this embodiment, it should be understood that allembodiments herein can be configured to support rotation about axis 324,as well. A rotating fixation plate, for example fixation plate 266, canbe provided in this embodiment, as with other embodiments of thedisclosure.

Implants of the disclosure enable a continuous expansion and retractionover a range of displacements according to predetermined dimensions of aspecific spacer 100 design. This provides the ability to distractvertebral bodies to a desired height, but also to collapse the spacer100 for repositioning, if therapeutically advantageous for the patient.Endplates 110, 112 may be shaped to form planes or surfaces whichconverge relative to each, to provide for proper lordosis, coronalcorrection, or kyphosis and can be provided with openings through whichbone may grow, and into which bone graft material may be placed. Spacer100 may be used to distract, or force bones of a joint apart, or may beused to maintain a separation of bones created by other means, forexample retractor. Endplates 110, 112 may additionally be curved toconform to the surface of body tissue, for example the surface ofcortical bone, of the vertebra to be contacted, for improved fixationand load bearing.

Spacer 100 may be fabricated using any biocompatible materials known toone skilled in the art, having sufficient strength, flexibility,resiliency, and durability for the patient, and for the term duringwhich the device is to be implanted. Examples include but are notlimited to metal, such as, for example titanium and chromium alloys;polymers, including for example, PEEK or high molecular weightpolyethylene (HMWPE); and ceramics. There are many other biocompatiblematerials which may be used, including other plastics and metals, aswell as fabrication using living or preserved tissue, includingautograft, allograft, and xenograft material.

Portions or all of the implant may be radiopaque or radiolucent, ormaterials having such properties may be added or incorporated into theimplant to improve imaging of the device during and after implantation.

For example, metallic portions 124, 124A of endplates 110, 112 may bemanufactured from Titanium, or a cobalt-chrome-molybdenum alloy,Co—Cr—Mo, for example as specified in ASTM F1537 (and ISO 5832-12). Thesmooth surfaces may be plasma sprayed with commercially pure titanium,as specified in ASTM F1580, F1978, F1147 and C-633 (and ISO 5832-2).Polymeric portions 122, 122A may be manufactured from ultra-highmolecular weight polyethylene, UHMWPE, for example as specified in ASTMF648 (and ISO 5834-2). In one embodiment, PEEK-OPTIMA (a trademark ofInvibio Ltd Corp, United Kingdom) may be used for one or more componentsof spacer 100. For example, polymeric portions 122, 122A can be formedwith PEEK-OPTIMA, which is radiolucent, whereby bony ingrowth may beobserved. Other polymeric materials with suitable flexibility,durability, and biocompatibility may also be used.

In accordance with the invention, implants of various sizes may beprovided to best fit the anatomy of the patient. Components of matchingor divergent sizes may be assembled during the implantation procedure bya medical practitioner as best meets the therapeutic needs of thepatient, the assembly inserted within the body using an insertion tool.Implants of the invention may also be provided with an overall angulargeometry, for example an angular mating disposition of endplates 110,112, to provide for a natural lordosis, or a corrective lordosis, forexample of from 0° to 6° for a cervical application, although muchdifferent values may be advantageous for other joints. Lordotic anglesmay also be formed by shaping one or both of plates 110, 112 to haverelatively non-coplanar surfaces. Expanded implant heights, for use inthe vertebrae for example, may typically range from 3 mm to 25 mm, butmay be larger or smaller, including as small as 2 mm, and as large as 30mm, although the size is dependent on the patient, and the joint intowhich an implant of the invention is to be implanted. Spacers 100 may beimplanted within any level of the spine, and may also be implanted inother joints of the body, including joints of the hand, wrist, elbow,shoulder, hip, knee, ankle, or foot.

In accordance with the invention, a single spacer 100 may be used, toprovide stabilization for a weakened joint or joint portion.Alternatively, two, three, or more Spacers 100 may be used, at a singlejoint level, or in multiple joints. Moreover, Spacers 100 may becombined with other stabilizing means.

Additionally, spacer 100 may be fabricated using material thatbiodegrades in the body during a therapeutically advantageous timeinterval, for example after sufficient bone ingrowth has taken place.Further, spacer 100 is advantageously provided with smooth and orrounded exterior surfaces, which reduce a potential for deleteriousmechanical effects on neighboring tissues.

Any surface or component of the invention may be coated with orimpregnated with therapeutic agents, including bone growth, healing,antimicrobial, or drug materials, which may be released at a therapeuticrate, using methods known to those skilled in the art.

Devices of the disclosure provide for adjacent vertebrae to be supportedduring flexion/extension, lateral bending, and axial rotation. In oneembodiment, spacer 100 is indicated for spinal arthroplasty in treatingskeletally mature patients with degenerative disc disease, primary orrecurrent disc herniation, spinal stenosis, or spondylosis in thelumbosacral spine (LI-ST). Degenerative disc disease is advantageouslydefined as discogenic back pain with degeneration of the disc confirmedby patient history and radiographic studies, with or without leg(radicular) pain. Patients are advantageously treated, for example, whomay have spondylolisthesis up to Grade 2 at the involved level. Thesurgery position spacer 100 may be performed through an Anterior,Anterolateral, Posterolateral, Lateral, and/or posterior approach.

In a typical embodiment, spacer 100 has a uncompressed height, beforeinsertion, of 2 to 25 mm, and may advantageously be provided incross-sections of 23×32 mm, 26×38 mm and 26×42 mm, with 4, 8, 12, or 16degree lordotic angles, although these are only representative sizes,and substantially smaller or larger sizes can be therapeuticallybeneficial. In one embodiment a spacer 100 in accordance with theinstant disclosure is sized to be inserted using an MIS approach (areduced incision size, with fewer and shorter cuts through body tissue).

Spacer 100 may advantageously be used in combination with other known orhereinafter developed forms of stabilization or fixation, including forexample rods and plates.

All references cited herein are expressly incorporated by reference intheir entirety. There are many different features to the presentinvention and it is contemplated that these features may be usedtogether or separately. Unless mention was made above to the contrary,it should be noted that all of the accompanying drawings are not toscale. Thus, the invention should not be limited to any particularcombination of features or to a particular application of the invention.Further, it should be understood that variations and modificationswithin the spirit and scope of the invention might occur to thoseskilled in the art to which the invention pertains. Accordingly, allexpedient modifications readily attainable by one versed in the art fromthe disclosure set forth herein that are within the scope and spirit ofthe present invention are to be included as further embodiments of thepresent invention.

What is claimed is:
 1. A spacer for maintaining a separation of bones ofa joint, comprising: a frame; a carriage slideably coupled to the frameand having distal and proximal ends defining a longitudinal axisextending therebetween, the carriage having at least one ramped surface;a first endplate configured to engage a first bone of the joint, andhaving at least one first surface mateable with the at least one rampedsurface; and a second endplate configured to engage a second bone of thejoint; an expansion cam disposed between the first and second endplates;a shaft coupled to the frame and the expansion cam such that rotation ofthe shaft causes the expansion cam to rotate, which in turn causes thefirst endplate to move along an axis transverse to the longitudinal axisto increase a height between the first and second endplates while thefirst endplate is being guided by the at least one first surface matedwith the at least one carriage ramped surface.
 2. The spacer of claim 1,wherein the carriage includes at least two ramped surfaces, and thesecond endplate includes at least one second surface mateable with atleast one of the two ramped surfaces of the carriage, whereby when theshaft rotates the expansion cam, the second surface slides against theat least one of the two ramped surfaces.
 3. The spacer of claim 1,wherein the first endplate includes a first proximal wall extendinglaterally to the longitudinal axis, the first proximal wall including atleast one aperture through which a fastener may pass to secure the firstendplate to a bone of the joint.
 4. The spacer of claim 3, wherein theproximal further includes a blocker that prevents backing out of afastener passed through the first endplate.
 5. The spacer of claim 1,wherein the first endplate is composed of two interconnected portions ofdissimilar materials.
 6. The spacer of claim 5, wherein one dissimilarmaterial is polymeric, and another dissimilar material is metallic. 7.The spacer of claim 1, further including a plate extending laterally tothe longitudinal axis and having at least one aperture sized anddimensioned to receive an elongated fastener for fastening the plate tobone of the joint, the plate being releaseably detachable from the frameto reduce a profile of the spacer during insertion of the spacer intothe body, the plate adapted to attach to the frame inside the body. 8.The spacer of claim 1, wherein the first endplate includes a rotatableportion having first and second transverse axes of different lengths. 9.The spacer of claim 8, wherein the rotatable portion is passable throughan interior of the spacer.
 10. The spacer of claim 1, wherein the firstendplate includes an aperture sized and dimensioned to receive anelongated fastener operable to pass through the aperture to affix theendplate to bone of the joint, the aperture movable with the firstendplate as the first endplate is moved along the axis transverse to thelongitudinal axis.
 11. The spacer of claim 1, further including at leastone rotatable plate having an aperture through which a fastener may passto secure the spacer to a bone of the joint, the rotatable platerotatable after the spacer has been implanted within the body, tooverlie the aperture with bone of the joint.
 12. The spacer of claim 1,wherein the at least one ramped surface is adapted to push a piercingelement through an aperture in the first endplate, the piercing elementoperative to pierce a bone to secure the spacer within the body.
 13. Thespacer of claim 1, further comprising: at least one elongate rotatabledeployer pivotally connected to the frame; at least one piercing elementconnected to the deployer, the at least one piercing element operable topierce bone of the joint when the rotatable deployer is rotated withinthe body.
 14. A spacer for maintaining a separation of bones of a joint,comprising: a frame; a carriage slideably coupled to the frame andhaving distal and proximal ends defining a longitudinal axis extendingtherebetween, the carriage having at least one ramped surface; a firstendplate configured to engage a first bone of the joint and having afirst proximal wall extending laterally to the longitudinal axis from aproximal end of the first endplate, the first endplate having at leastone first surface mateable with the at least one ramped surface, thefirst proximal wall including at least one aperture through which afastener may pass to secure the first endplate to a bone of the joint; asecond endplate configured to engage a second bone of the joint; anexpansion cam disposed between the first and second endplates; a shaftcoupled to the frame and the expansion cam such that rotation of theshaft causes the expansion cam to rotate, which in turn causes the firstendplate to move along an axis transverse to the longitudinal axis toincrease a height between the first and second endplates while the firstendplate is being guided by the at least one first surface mated withthe at least one carriage ramped surface.
 15. The spacer of claim 14,wherein the first proximal wall is a metallic portion and a portionextending longitudinally along the longitudinal axis is a polymericportion attached to the metallic portion via a screw.
 16. The spacer ofclaim 14, wherein the first endplate includes a rotatable portion havingfirst and second transverse axes of different lengths.
 17. The spacer ofclaim 16, wherein the rotatable portion is passable through an interiorof the spacer.
 18. The spacer of claim 14, wherein the at least oneramped surface is adapted to push a piercing element through an aperturein the first endplate, the piercing element operative to pierce a boneto secure the spacer within the body.
 19. The spacer of claim 14,further comprising: at least one elongate rotatable deployer pivotallyconnected to the frame; at least one piercing element connected to thedeployer, the at least one piercing element operable to pierce bone ofthe joint when the rotatable deployer is rotated within the body.